1. Field of the Invention
The invention relates generally to logging instrumentation for oil field wells, and more particularly to methods and instruments that can communicate topside over a standard, non-insulated slickline from substantial exploration depths.
2. Description of the Prior Art
The oil-field industry uses two basic types of logging methods to explore oil and gas wells, e.g., slickline and wireline. Dropping a series of sensing tools, such as porosity tools, gamma tools, pipe-collar detectors, etc. Getting the info out of the hole.
Wireline has a large-diameter cable that mechanically supports the hanging instrument. A wireline truck on the surface is required in support, and such is large and expensive. A data cable supplies power and provides a communication connection down the well to the instrument. But wireline data cable is very difficult to use in high-pressure wells because of its large diameters. The pressure on the well will work across the entire diameter at the top seals, so at high pressures only thin monofilaments are practical to seal.
Slickline techniques are used. But they are not real-time, and data is recorded in memory that is later read-out on the surface. Battery power only. Solid wire ⅛ inch to 60/1000 inch, e.g., like piano-wire. Tool string can weigh 200 pounds, and such weigh may not be enough to pull the whole down given the well. Only the cable depth is provided. If the logging discovered something interesting, the whole procedure must be repeated.
Slickline logging tools have been developed in recent years to enable data collection in deep oil and gas wells. The well casing is completed by setting pipe and grouting it in place with cement. The cement seals the annulus between the soil and the outside diameter of the pipe. The top of the pipe is threaded and a blow-out preventer is screwed on. Such closing valve and a second pipe provide a sealable standpipe. The standpipe is long enough to accommodate a logging tool with a top sub attached to the slickline cable. The cable exits a lubricator through a sealing gland that enables the slick line to enter the sealed standpipe under pressure. When the gate valve is fully opened, the logging tool descends into the well casing, maintaining a seal with the slick line as the hoist lowers the logging tool into the holes.
Conventional slickline logging tools are designed with internal recording memory to log data during descent and ascent in the hole. After returning from the well, recorded digital data is read out on the surface and chart recordings are used to display the data for analysis.
What is needed is a data communication system that can support real-time data transmissions of oil-field logging instrumentation over conventional non-insulated solid-wire slicklines.